Distributed monitoring systems typically comprise multiple agents collecting data over time. The agents need to send reports or other types of updates periodically or upon request to a central server where the concentration of information may reveal important aspects of the system being monitored. Some examples of where this type of updating may be necessary include communication network monitoring and analysis, distributed call center monitoring, and monitoring of processing systems or sensor networks.
A problem that can arise in these and other distributed monitoring environments is that the transmission of reports or other updates from the distributed agents to the central server can consume an excessive amount of resources when the number of agents is very large or when the resources are very scarce. For example, in a network monitoring and analysis system involving a large number of endpoint devices, the communications of the endpoint devices with a central controller or other central server can represent a significant traffic burden on the network. As another example, sensor agents may have only very limited power supply capacity, and so their communications with a central server should be limited so as to conserve this scarce resource.
A known technique for reducing the amount of data sent from agents to a central server in the context of monitoring networked applications is disclosed in J. M. Chambers et al., “Monitoring Networked Applications with Incremental Quantile Estimation,” Statistical Science, January 2006. In this approach, agents send partly summarized data to a central server where the aggregation of the various summaries takes place. Each agent fills a data buffer D of size N. When D is full, a quantile buffer Q is updated and D is flushed. Periodically or upon request, Q is sent to the server for aggregation.
It is possible in certain monitoring systems to avoid the use of a central server altogether. An example of a fully distributed monitoring system of this type is disclosed in U.S. Pat. No. 7,031,264, issued Apr. 18, 2006 in the name of inventors A. Adhikari et al. and entitled “Distributed Monitoring and Analysis System for Network Traffic,” which is commonly assigned herewith and incorporated by reference herein. In an illustrative embodiment, the agents comprise endpoint devices that collect and process measurement data relating to Voice over Internet Protocol (VoIP) communications, multimedia communications or other types of network traffic. The endpoint devices are advantageously configured to operate in a manner that does not require the use of a centralized controller or other central server.
Despite the above-described techniques, a need remains for further improvements in distributed monitoring involving a central controller or other type of central server, particularly with regard to limiting the frequency at which agents transmit reports or other updates to the central server.